Recently, along with development of medical techniques, high sensitivity, high image quality and high-speed processing for reducing stress on patients and improving handling are desired in X-ray photographic materials for use in medical diagnosis. To achieve rapid processing, in particular, further enhancement of developability and drying speed is desired.
In response to these requirements are proposed a variety of techniques for rapid access. In photographic materials, for example, is a technique of using tabular silver halide grains, whereby covering power, spectral sensitivity, sharpness and graininess are known to be enhanced. Presumably due to the shape of the tabular grains, on the other hand, fine filaments of developed silver are easily extended to form yellowish silver images, which reduce accuracy of diagnosis.
There is known, as means for improving silver image tone, enhanced hardening of the photographic material, which, however, adversely affects developability and fixability in rapid processing. There is also known a means for improving silver image tone by allowing a compound such as 1-phenyl-5-mercaptotetrazole to be incorporated into a silver halide emulsion layer. However, this causes disadvantageous lowering of the sensitivity. Further, JP-A 3-153234 (hereinafter, the term "JP-A" refers to unexamined and published Japanese Patent Application) discloses the use of a leuco dye, which forms imagewise a blue dye in proportion to developed silver. This technique, however, was proved to be insufficient in blue color formation. Specifically in the case of rapid access, in which the total processing time from development to drying is 30 sec. or less, blue color formation was insufficient and silver image tone was not improved to acceptable practical level. Accordingly, there is desired a photographic material with superior sharpness and improved silver image tone, even when subjected to rapid processing.